Single-cylinder eccentric actuated pump

ABSTRACT

A pump-motor set comprising a reciprocating cylindrical pump for use with an electric motor having a cylindrical flange and a drive shaft projecting centrally of the flange. The pump has a body formed with a cylinder in which a piston slides to move fluid from an inlet to an outlet. The piston has a length such as to protrude from the bottom of the pump body and the latter is mounted directly on the flange of the motor. An eccentric is secured directly to the tip of the motor shaft so as to be in contact with the free end of the piston. Thus, rotation of the shaft causes reciprocation of the piston and operation of the pump.

United States Patent Jean Louis Gratzmuller 66 Blvd. Maurice Barres, 92 Neuilly-sur- [72] Inventor [54] SINGLE-CYLINDER ECCENTRIC ACTUATED [56] References Cited UNlTED STATES PATENTS 1,995,424 3/1935 Guinness 103/57 X 2,358,612 9/1944 Acker 210/222 2,770,972 11/1956 Gratzmuller 103/213 X 2,900,839 8/1959 Mackintosh 103/213 X 2,919,591 l/l960 Watson 103/213 X 2,980,024 4/1961 Pope 103/57 X Primary Examiner- Robert M. Walker Attorney-Jacobi, Lilling & Siegel ABSTRACT: A pump-motor set comprising a reciprocating cylindrical pump for use with an electric motor having a cyiindrical flange and a drive shaft projecting centrally of the flange. The pump has a body formed with a cylinder in which a piston slides to move fluid from an inlet to an outlet. The piston has a length such as to protrude from the bottom of the pump body and the latter is mounted directly on the flange of the motor. An eccentric is secured directly to the tip of the motor shaft so as to be in contact with the free end of the piston. Thus, rotation of the shaft causes reciprocation of the piston and operation of the pump.

Patented Aug. 3, 1971 3,597,119

5 Sheets-Sheet 1 Patented Aug. 3, 1971 5 Sheets-Sheet 2 Patented Aug. 3, 1971 5 Sheets-Sheet. 5

atented Aug. 3 W71 5 sheets sheet 5 SINGLE-CYLINDER EGCENTRIC ACTUATED PUMP The present invention relates to a single-cylinder pump actuated by an eccentric for use, for instance, as a source of pressure fluid in hydraulic control systems.

Pumps of this type heretofore known generally comprise a shaft rotatable in bearings carried by a case solid with a pump body and over which an eccentric, actuating the pump piston, is keyed. The pump shaft is coupled either directly or through a transmission to a motor such as an electric motor.

Such pumps are relatively costly to manufacture due to the presence of the shaft, of the bearings and of the alignment of the various members. The cost of these pumps is particularly high if it is compared to that of the electric motors that drive them and particularly the standard motors that are mass produced.

The present invention makes it possible to obtain pumps of this type that are much more economical than in the past.

In a pump according to the invention, the pump body is made to be secured directly on the flange of an electric motor, particularly of the standard type, and the eccentric of the pump rather than being keyed to a shaft which is part of the pump rather than being keyed to a shaft which is part of the pump is keyed directly on the tip of the motor shaft. With such an arrangement, the pump itself does not have any shaft nor bearings since the motor shaft and bearings themselves are used. An important saving is thus realized, all the more as the shaft case of the pump as well as the preferably resilient coupling between the pump shaft and the motor shaft are also eliminated.

An object of the invention lies in the provision of a singlecylinder pump actuated by an eccentric and comprising a pump body, a rodlike piston slidable in a cylinder provided in the pump body, return means for the piston, a fluid inlet and outlet within and outside the pump body as well as suction and discharge stop valves, the said pump further having the following features: the free end of the rod like piston extends beyond the pump body; the pump body comprises members and surfaces for directly securing the pump body on the flange of an electric motor; an eccentric, directly keyed on the motor shaft, cooperates with the free end ofthe rodlike piston.

The pump according to the invention has the advantage that it can be mounted on standard motors that are not costly, that is it is not necessary to use special motors that are more costly.

On standard motors, the securing flanges are standardized as well as the shaft tips or ferrules so much so that the pumps according to the invention are completely interchangeable.

On the other hand, the pumps according to the invention comprise certain other particular features (proportions of the piston stroke, of the discharge pressure, of the piston surface, as regards the motor characteristics such as starting torque, nominal torque, permissible bearing load) that give to the pump-motor set the optimum dependability despite the particular conditions imposed upon the motor shaft that has to work in overhang.

A pump according to the invention is of course suitable for any desired flow as well as any desired pressure provided the various elements are properly dimensioned and the tip propriate motor is selected. However, as will be seen later on, the motor is best used in the case where the pump is adapted to discharge under high pressure, for instance above 100 kg./cm.'- and namely for pressures greater than 200 or 300 kgJcmF. As a result, a pump-motor set of this type is particularly adapted for hydraulic control systems, such as hydraulic controls for circuit breakers.

The pumps according to the invention may further and preferably comprise other features intended to improve the operation, particularly in the case of high-pressure pumps where air is contained in the liquid being pumped.

Pumped fluids indeed often contain dissolved air that may escape at rest as when cooling is produced, it being understood that the solubility of air increases with temperature.

Besides, it is necessary with such pumps to use elements for filtering the fluid. Now, it is known that filters prevent air from passing through and returning to the tank. On the other hand, there is always a pressure loss due to the filter and a relative vacuum is created between the suction valve and the filter. There is therefore an advantage to mount the filters as close as possible to the valves and to immerse the set while avoiding any coupling that may cause air to enter.

By various constructional features, the present invention overcomes these disadvantages and provides these requirements.

An object of the present invention is also to provide a piston pump comprising a casing in permanent communication with a loaded tank and a cylinder within which a piston is displaced which, alternatively, sucks fluid from the said casing into the cylinder and discharges it from the cylinder into the discharge circuits, pump which is characterized by the fact that the cylinder in which the piston is displaced forms a cover for the casing and comprises a housing for the block comprising the suction and discharge conduits.

This general arrangement obviously appreciably reduces the dead spots. On the other hand, it makes it possible to immerse the suction valve in the fluid outside the zone where air bubbles could accumulate. Finally, the machining in a single block of a certain number of mechanical component parts of the pump results in an important reduction in the cost of such a pump.

Finally, in order to improve the evacuation of the air contained in the liquid, the suction conduit of a pump according to the invention, that is the conduit that connects the body of the pump and the loaded tank, is preferably a conduit that is inclined in relation to the vertical on at least a portion of its length.

The invention will be better understood from the following detailed description having reference to the appended drawings that represent, by way of nonlimitative examples, various embodiments of the invention.

FIG. 1 is a cross-sectional view of a pump according to the invention mounted on the flange ofa standard motor;

FIG. 2 is an elevation view of the pump, viewed from the side opposite the motor;

FIG. 3 is a side elevation view of the pump, viewed from the side of the motor;

FIG. 4 is a cross-sectional view of another embodiment of the pump according to the invention;

FIG. 5 is a view in elevation of the pump, viewed from the opposite side of the motor, illustrating the mounting of the pump on the flange of a standardized motor;

FIG. 6 is a diagram illustrating the forces that the transmits to the shaft and to the motor bearings;

FIG. 7 is an end view of a pump-motor set comprising two single-cylinder pumps according to the invention mounted on the flange of the same motor and actuated by a common eccentric;

FIG. 8 is a cross-sectional view of an embodiment illustrating a different mounting of the eccentric on the ferrule of the motor shaft;

FIG. 9 is a partial cross-sectional view illustrating the mounting of the filter in a pump according to the invention;

FIG. 10 is a cross-sectional view of another embodiment of a pump comprising the particular arrangement for the discharge ofthe air contained in the pumped liquid.

In the embodiment illustrated in FIG. I, the pump comprises a pump body 1 within which a cylinder 3 is mounted in which a rodlike piston 5 slides. The pump also comprises a hydraulic fluid inlet means 7 and a pressure fluid discharge means 9 cooperating respectively with an inlet ball valve 11 and a discharge ball valve 13, these two valves being fixed in the body of the pump above the cylinder 3 and being maintained clamped by a screwcap 15 in which the discharge orifice 9 of the pump is provided.

The pump may also comprise an auxiliary fluid inlet 17 in communication with a groove 23 cut out of the rodlike piston 5 by an annular passage 19 between the pump body I and the cylinder 3 and by a conduit 21. This fluid inlet establishes an annular liquid seal between the piston 5 and the cylinder 3. The auxiliary fluid may be the pumped fluid itself. A pump of this type has been described namely in French Pat. No. 1,074,] granted to the same inventor.

According to the invention, the free end 25 of the rod like piston 5, that is the end opposite the compression chamber, extends beyond the lower portion of the pump body 1. In the case where the pump body does not completely cover the lower part of cylinder 3, this piston 5 extends downwardly outside cylinder 3. On the other hand, the pump body 1 comprises members and surfaces for directly securing the pump body on the flange 27 of an electric motor 29, namely a motor of the standard type. The securing members aforesaid may be constituted by two lugs 31, 31 that project from the body of the pump and that can be applied against the radial surface of the flange 27 of the motor (FIGS. 2 and 3). Orifices 33, 33 drilled through lugs 31, 31 with a standard spacing receive screws 35,35 that screw into corresponding threaded holes in the flange of the motor. The lugs are connected together by a flat surface 38 (FIG. 3) level with the plane of the lugs, surface 38 bearing uniformly against the flat surface facing the flange to resist the bending forces of the fixing of the pump on the motor, these forces resulting from the hydraulic pressure on the piston which is transmitted to the eccentric connected to the motor shaft. The pump body 1 also has surfaces for securement on the flange, these surfaces having a shape mating with the shape of the flange. It is thus that a shoulder 37 is preferably provided in the pump body, the shoulder having a cylindrical surface adapted to bear against the cylindrical upper surface of the flange 27, this shoulder easing the positioning ofthe pump on the motor flange.

With these various securing means, the pump may be mounted with accuracy and solidly secured, in an interchangeable manner, on any standard motor.

Finally, the pump according to the invention comprises an eccentric 39 directly fixed on the standard tip 41 of the shaft of motor 29. This eccentric 39 actuates the rodlike piston 5 through the use ofa ball bearing 43, preferably of the impervious type. A pump according to the invention may also comprise a return spring for the rodlike piston which has not been illustrated in FIG. 1, being assumed for instance that this is the case of a pressurized pump, that is one supplied with liquid at a pressure greater than atmospheric pressure.

Of course, sealing joints are provided as is usual? between the various components 3, 11, 13 and of the pump.

As can be seen from the preceding description, the pump according to the invention does not comprise any ball bearing, nor shaft, nor casing housing the bearings and the shaft, nor elastic or nonelastic coupling between the motor and the pump, as all of these elements are either eliminated or else are parts of the motor.

Standard motors of the leg and flange type are preferably used wherein the legs allow the pump-motor set to be put into position directly and economically.

The pump according to the invention illustrated in FIG. 4 comprises the same essential elements as those of the pump described with reference to FIG. 1 except that the pump body 1 forms a fluidtight casing defining an inner chamber 47 in which a hydraulic fluid inlet 7' opens. On the other hand, the rodlike piston of the pump is made up of two parts mounted end to end, that is, a piston rod proper 49 sliding in the cylinder 3' and a push rod 51 extending across the bottom wall 53 of body 1' through a sealing joint 55, the latter being preferably mounted in a groove formed in the body of the pump. Because of this two-part arrangement of the piston rod, no problem arises as to the alignment between the bore of the cylinder 3' and the passage of the push rod 51 through the bottom 53 of the body 1.

A particularly advantageous arrangement of pump section and discharge valves have also been illustrated in FIG. 4.

According to this arrangement, the cover 57 constitutes a downwardly extended part compactly comprising on the one hand, the bore 109 within which the piston 49 reciprocates, on the other hand, a central housing 117 in which is located a unit 59 structurally comprising the valve piece and the conduits allowing fluid passage from inner chamber 47 to the discharge space 119, on the other hand, the union between the discharge zone 119 and the outlet conduit 121.

Unit 59 is drilled with two or several conduits 124 and 125. The latter communicates with inner chamber 47 through lateral channels 126. A filter 127, the features of which are described hereinafter, is located immediately in front of the orifices of the channels 126. Conduits 124 and are closed by valves such as ball valves 128, 129 herein shown, the movements of which are limited by short rods and 131 and are guided laterally into cylindrical surfaces.

The pump illustrated in FIG. 4 also comprises a return spring 61 for the rodlike piston as well as a magnetic plug 63 for the collection of impurities at the bottom of the pump body.

In a pump according to the invention, it is advantageous to be able to center the bearing 43 in relation to the rodlike piston, particularly in the case where the bearing 43 is an impervious bearing having a single row ofballs. Means for axially adjusting the eccentric 39 on the tip of shaft 41 is provided to obtain this centering.

This adjusting means may be constituted (FIG. 1) by a first ring 65 hearing on one side against a shoulder 67 of the tip of the shaft 41, the eccentric 39 being clamped between the ring 64 and a second ring 69 by means of a washer 71 and of a screw 73 threaded into the tip of the standard shaft. To center the eccentric and consequently the bearing 43 in relation to the rodlike piston, it is sufficient to select a ring 65 having the appropriate width.

According to another embodiment (FIG. 4), this adjusting means may be simply made up of a setscrew 74 threading through the eccentric 39 and bearing against the shaft tip. In this embodiment, it is only necessary to slide the eccentric on the shaft tip right up to the desired position and then to tighten the screw 74.

'The eccentric 39 illustrated in FIGS. 1 and 4 is made solid with the tip of shaft 41 of the motor for rotation therewith by means of a key 89 located in the keyway of the shaft tip. On the other hand, it has been indicated that the pump comprises means for axial adjustment of the eccentric 39 on the shaft tip. This means has a great importance as it allows perfect centering of the ball bearing 43 in relation to the rodlike piston 5, or to push rod 51, thus considerably reducing the wear of the ball bearing particularly in the case where a rigid impervious bearing having a single row ofballs is used.

With reference to the embodiment illustrated in FIG. 8, common means is used to simultaneously ensure fastening of the eccentric on the shaft tip for rotation and axial adjustment and securement of the eccentric in the position corresponding to the desired centering of the bearing. This solution is thus more economical than that wherein a key is used.

According to this embodiment, these common elements are constituted by two setscrews 79, 79' respectively screwed on either side of the bearing 43, in two threaded holes in the thick portion of the eccentric 39.

According to one embodiment, the two setscrews 79, 79' may bear against the bottom of the keyway of the shaft tip but according to the more general embodiment illustrated in FIG. 8, the two setscrews merely bear against the cylindrical surface of the shaft tip, that is outside the keyway 81, the latter being for instance located at 90 in relation to the plane containing the axes of the screws 79, 79'.

The said screws being in contact with the cylindrical surface of the shaft on an annular friction surface having a relatively large mean diameter cannot be loosened and the securement of the eccentric, with the possibility of axial adjustment, is perfectly assured.

To facilitate the mounting and the adjustment into position of the eccentric 39 on the tip of the shaft 41, a slight clearance 83 may be provided between the eccentric andthe shaft rather than tightly clamp the eccentric on the shaft. The cost of machining is reduced by the same token. Of course, in such a case when the setscrews are tightened, the eccentricity of the eccentric is slightly increased in relation to the theoretical eccentricity but this presents no inconvenience since it is only in the order ofa tenth ofa millimeter.

With an assembly of this type, motors can be used in which the tip of the shaft has no keyway or in which the keyway is too short in relation to the eccentric.

The assembly is carried out by simply solidly fixing the bearing 43 over the eccentric 39, to screw the setscrews 79, 79' into their threaded holes, then to slip the assembly over the tip of the shaft 41. The assembly may then be slid axially until the bearing 43 is centered in relation to the push rod 51 and is then definitely secured by the setscrews 79,79.

Another improvement, also illustrated in FIG. 8, makes it possible to increase the protection against wear of the sealing ring or packing 55 intended to provide sealing during the passage ofthe push rod 51 (or of the rodlike piston in the case where there are no push rods) through the bottom 53 of the pump body. Indeed as has been seen previously, a filter 127 is preferably provided around the valve block 59 in a pump made according to the invention. However, this filter will not protect the sealing ring 55 so much so that certain impurities may escape the attraction of the magnetic plug 63 and will become caught between the push rod and the O-ring 55.

The present improvement resides in providing, above the sealing ring 55, a so-called *raking" ring 87 the lip or skirt of which clings to the outer surface of the push rod and prevents the impurities from reaching the toroidal ring 55. This raking ring may be metallic but it will preferably be made of elastomeric material capable of resisting the pump fluid.

FIG. 5 illustrates the simple manner of mounting a singlecylinder pump according to the invention on the flange 27 ofa motor 29. The first lug 31 of the pump being first connected to the flange 27 by a screw 35, loosely screwed, the body 1 of the pumpis pivoted in the direction of the arrow A to bring the hole 33' in registry with the corresponding hole 75 of the flange. The screw 35' is then set into position without screwing it completely, then the body of the pump is lowered so that the shoulder 37 bears on the top of the flange and there only remains to definitely tighten the screws 35, 35'.

Certain particular features of the pump according to the invention will be indicated in the following description, having reference to FIG. 6 These features will take into account the fact that the tip ofthe motor shaft works in overhang.

It may however be said immediately, by way of example, that a pump according to the invention intended for a flow of 1,301 emf/minute under a pressure of 336 bars may be mounted on a standard electric motor with legs and flange of2 hp. at 3,000 r.p.m., such a motor having a standard flange F l according to standard NF 51.150 and having a shaft the tip of which conforms to standard NF 51.105.

The above description always referred to single-cylinder pumps but it should be understood that it is possible to mount a plurality ofidentical pumps on the flange of the same motor, for instance two pumps acting in opposition, the rodlike pistons of which are actuated by a common eccentric mounted on the shaft ofthe motor (FIG. 7).

The ratio of the starting torque to the nominal torque, for the electric motors used, being comprised between 1.8 and 2, for the electric motors used, being comprised between 1.8 and 2, there results that with a pump-motor set comprising two identical pumps acting in opposition, twice the flow under substantially identical pressure may be obtained while using the same motor as in the case where there is a single pump. The motor is thus used at full load both upon starting and during normal operation. Upon starting, the two opposed pumps have their load torques out of phase by 180. Thus, the starting torque'is not increased as compared to a pump-motor set having only one single pump.

On the other hand, the standard flanges being provided with four holes at are particularly adapted to receive a single pump or two pumps in opposition, the lugs being suitable as well for the two cases.

As has been said previously, one of the main advantages of the invention resides in the fact that the pump may be mounted on standard motors. As has also been seen, the pump forces the motor shaft and, more specifically still the motor bearings, to operate under particular conditions due to the overhanging force acting on the tip of the shaft.

Any change made to the motor, and namely to its bearings, to suit these particular working conditions would destroy the desired economic advantage. That is the reason why, in a pump according to the invention, certain noteworthy constructional and dimensional features have been provided that will be described hereinafter with reference to FIG. 6.

The force F, due to the discharge pressure p of the liquid on the surface s of the piston and to the force of the return spring of the piston, is transmitted to the shaft 41 by means of the push rod 51 of the eccentric bearing 43 and of the eccentric 39. The bending resistance of the shaft 41 of a standard motor under this load being greater than the resistance of the standard front bearing 77 under the said force, it isthe latter that is one of the factors allowing the determination of the maximum permissible force F.

The determining characteristic of the motor allowing dimensioning of the pump is the starting torque Cd of the motor. If the stroke of the piston of the pump hasa value I, the 1 pump having the maximum product flow x pressure" that the motor will be able to start up will be such that:

(l) FXl/2l=Cd If, in order to obtain the desired operating life, for instance 500 or 1,000 hours without inspection, the standard front bearing 77 of the motor may support a maxim-um load P, which is a characteristic of the selected motor, it is seen from FIG. 6 that the permissible force F will be:

, lis

Cd and P being known characteristics of the motor, the stroke 1 of the piston may be derived from the equations (1) and (2):

(3) Cd B it being understood that P depends on the number-of permissible operating hours for the pump-motor set before inspection.

The ratio B/A (FIG. 6) of the lever arms being, in practice, of the order of 1.25, there follows that:

12 2.5 CD/P As it is generally advantageous to have the motors rotate at 3,000 r.p.m. (50 cycles) or 3,600 r.p.m. (60 cycles), rather than at 1,500 or 1,800 and for considerations of vibrations and fatigue in the return stroke of the piston, there is an advantage to select the shortest possible stroke, that is to select the shortest possible stroke, that is to select it close to:

2.5 Cd/P In other words, in a pump according to the invention it is possible to say that: the pump body is secured over the standard flange of a motor; the piston is actuated by an eccentric mounted directly on the tip or ferrule of the standard shaft of the motor and that the stroke of the piston is at least equal to, and preferably close to, 2.5 times the ratio of the starting torque of the motor to the force that the motor shaft bearing applies on the said tip or ferrule. 1

There will be given hereinafter an example of how a pump according to the invention is determined.

For a 1.5 h.p. standard motor rotating at 3,000 r.p.m., the starting torque is 0.7 m./kg. (1.8 times the nominal torque) the permissible load P on the front bearing is 271 kg. for an operating life of 1,000 hours, A= mm., B=2l5 mm. From formula If it is desired to have a pump discharging undera pressure p of 336 bars (343 kg./cm.'-) the surface s of the piston will be obtained from equation (4) ps F (load of the return spring of the piston) It has been seen that and, in the case where the return spring has a force of 30 kg, there is obtained:

that is the diameter of the piston must, at the most, be equal to 8.3 mm.

For such a pump, the flow will be 900 cm./min. at 3,000 rpm. under a pressure of 336 bars for a service life of 500 hours.

It may be noted that if maximum flow was desired with a pump adapted to such a motor, that is with a pump having a stroke of about 6.5 mm., the diameter of the piston would be limited to a value equal to about 1.5 times the stroke. In such a case, the piston surface would be approximately 0.75 cm.

If the load of the return spring is disregarded in equation (4), in order to simplify, then =0.54 cin.

P P ;2.. S. ..l1.? 2 which means that the pump may operate under a pressure in kg/cm. ofthe same order than the force in kg. that the standard bearing ofthe motor can withstand, that is, 271 kg. in the preceding example.

The result is that the pumps according to the invention are particularly appropriate as high-pressure pumps, for instance above 100 kg/cmfi and namely above 300 kg./cm..

In the case ofliquid pumps and particularly of high-pressure pumps, the problems caused by the escape of air or gas contained in the liquid must be accounted for.

It is known that often important quantities of air are dissolved in fluid, particularly under high pressure. As a result, this air tends to escape in the case of cooling causing the pump to run dry. The compact structure selected for the assembly of the properly hydraulic members of the pump and described in relation to H6. 4 makes it possible to avoid such risks. Indeed, the valves are thus immersed in the liquid beyond the zone where such air bubbles could accumulate. On the other hand, this structure also makes. it possible to substantially reduce the dead spots. These two features decrease the risk of the pump running dry in spite of the saving obtained with the reduction in the number of parts.

For the same purpose, the suction force of conduits 7' is voluntarily located as high as possible in the chamber 47. In this manner, the level of this port being always substantially higher than that of the suction valve, the air may escape from the fluid and never reaches the level of this suction valve. Similarly, the conduit 7' has a sufficiently large diameter to allow escape of the gas most easily.

As indicated above, filters 127 are generally used. These filters tend to retain the air in the mass of fluid between them and the valve. According to another feature of the invention, the filters are located as close as possible to the compact assembly formed by the cover and its inner elements in such a way that the volumes comprised between the filter or filters and the suction valve be as small as possible. In the same manner and according to the invention, filters 127 of very wide surfaces in relation to the cross section of the lateral conduits 126 bringing the fluids to the suction conduit will preferably be used to reduce the losses of pressure and the relative vacuum created.

These filters 127 are sieves in the form of tubes the useful portion of which is limited to the area 126, bearing upwardly on a shoulder 127' of the cover 57 but free at the lower end to allow assembly. lts tips are covered by overlapping elastomeric rings 134 acting both to seal it and secure it into position HO. 9).

Other improvements can be made to the pump according to the invention to improve the evacuation of the air contained in the pump liquid.

According to these improvements, the suction conduit of the pump that connects the body of the pump to a reservoir or tank of low-pressure liquid, is a conduit rising from the pump body toward the tank and is inclined in relation to the vertical on at least a portion of its extension.

ln order to obtain the most efficient evacuation or escape of the air bubbles drawn with the oil in the suction conduit, it appears natural to arrange at least a portion of this conduit vertically in order to facilitate the rising of the air toward the tank and to allow the air bubbles to reach the free level of the oil. This is how pumps under head of a feed tank have heretofore been arranged.

However, the present inventor has been able to determine that this arrangement is not very efficient and that a substantially more complete evacuation can be obtained with an inclined conduit, as will be explained hereinafter.

According to another feature, no oil filter is placed across the path of the oil between the feed tank and the pump body, the oil filter if any being arranged immediately upstream of the suction valve of the pump. Again with this arrangement, the escape of air is made easier.

FIG. 10 is a cross-sectional view of another embodiment of a pump according to the invention.

This figure shows a single-cylinder pump with eccentric and a hydraulic control system fed by the pump has been shown. This system 'may comprise for instance: an oleopneumatic accumulator 40; a hydraulic jack 42 the rod of which actuates the member to be controlled (not shown); at least one control valve illustrated by a three-way cock 44 for feed and discharge; a tank or reservoir 46 for the return of oil as well as connecting conduits 48,50, 52,54.

Feeding of the pump with low-pressure oil is made by a suction conduit 7', 56 that places the volume inside the pump body in communication with the tank 46. According to the invention, the suction conduit is not arranged vertically as shown in FIG. 4 but obliquely, the inclination ofthe conduit in relation to the vertical being preferably comprised, on at least a portion of its extension between the pump body and the tank, between 30 and 60.

With this arrangement, it is possible to take advantage of the difference in specific gravity between the pure oil and the oil having air bubbles, whether these air bubbles are very fine as when oil is emulsified or these bubbles are very large as when there has been air influx.

Oil containing containing air, which is lighter, moves against the upper portion of conduit 7, 56 and creates, against the wall of this conduit, an ascending stream 58 moving right up to the tank where the air bubbles may dissipate.

It may also be assumed that a wall effect, against the upper wall of the conduit, collects the fine bubbles to form larger bubbles that rise even more easily because of their volumes, while licking the wall.

inversely, the heavier oil that contains no air concentrates at a lower level and descends along the lower wall of the conduit to feed the chamber ofthe pump body.

To the contrary, in a suction conduit vertically or almost vertically oriented as has so far been the case, the air bubbles spread over the entire cross section of the conduit and their rise is hindered by the descending oil current that feeds the pump.

Finally, if the filtering of the oil is necessary to avoid the introduction of impurities in the pump and in the circuit to which the pump is coupled, it has been observed that the presence of a filter on the suction conduit hinders the evacuation of the air contained in the oilr Indeed, the air bubbles are held between the mesh of the filter and do not easily rise toward the tank.

That is the reason why the filter is arranged downstream of the suction conduit, for instance in the form of filter 27 located immediately upstream of the suction valve and already described in relation to FIG. 9. At such a location, oil flowing through the filter is already deprived of the air that it contained.

Preferably, the tip 60 of the suction conduit on the side of the tank (or the upper end of the conduit connected to the portion of the inclined tube solid with the pump body) extends beyond the bottom 62 of the tank in such a way as to form at the bottom thereof a settling volume for the impurities. This arrangement is particularly desirable in view of the fact that no filter is provided on the suction conduit itself.

lclaim:

1. in a reciprocating cylindrical pump for use with an electric motor having a casing formed with a cylindrical annular flange portion and a motor drive shaft journaled in bearings included in the casing and extending centrally of said flange portion, said pump having a body formed with a cylinder, a piston slidable in said cylinder, a fluid inlet, a fluid outlet and suction and discharge valves, the improvement comprising:

a. said piston having a length such that the free end thereof extends outwardly ofsaid pump body;

b. means on said pump body to secure it directly onto said cylindrical flange, and

c. an eccentric to be mounted directly on said motor shaft for reciprocating said piston as said shaft rotates.

2. A pump as claimed in claim 1 wherein said pump body has outer surfaces having a shape mating the shape of said motor flange; said surfaces constituting at least one portion of said means for positioning and directly securing said pump on said motor flange.

3. in a reciprocating cylindrical pump for use with an electric motor having a cylindrical flange and a drive shaft extending centrally of said flange, said pump having a body formed with a cylinder, a piston slidable in said cylinder, a fluid inlet, a fluid outlet and suction and discharge valves, the improvement comprising:

a. said piston having a length such that the free end thereof extends outwardly of said pump body;

b. means on said pump body to secure it directly onto said cylindrical flange; and

. an eccentric to be mounted directly on said motor shaft for reciprocating said piston as said shaft rotates;

d. wherein said pump body has outer surfaces having a shape mating the shape ofsaid motor flange;

. said surfaces constituting at least one portion of said means for positioning and directly securing said pump on said motor flange; and

. wherein said means for directly securing said pump body on said motor flange further comprises two lugs each drilled with a hole, the said holes being spaced by 90 in relation to the axis of the motor and wherein a bearing surface for said pump body on said flange is provided between said lugs.

4. A pump-motor set comprising:

a. at least one reciprocating cylindrical pump comprising:

a pump body;

a piston slidable in a cylinder defined by said pump body;

a fluid inlet and a fluid outlet, and

suction and discharge valves;

. an electric motor comprising:

a driving shaft and a casing having bearings therein ournaling said shaft, said casing including a cylindrical flange transverse with respect to said shaft, said shaft projecting from the center thereof;

. wherein said piston has a length such that the free end thereof extends outwardly of said pump body;

d. means on said pump body to secure it directly onto said cylindrical flange, and

e. an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates.

5. A pump-motor set as claimed in claim 4 wherein said eccentric is keyed directly onto the free end of said shaft and comprising a ball bearing mounted over said eccentric with means for the axial adjustment of said eccentric on said shaft; said adjusting means being constituted by means for mounting the said eccentric on said shaft to provide rotation thereof in unison.

6. A pump-motor set as claimed in claim 5 wherein said means for the axial adjustment and rotation mounting means comprise two setscrews threaded through said eccentric to bear against the free end of said shaft.

7. A pump-motor set as claimed in claim 6 in which said two setscrews bear against the outer cylindrical surface of said free end of said shaft.

8. A pump-motor set comprising:

a. at least one reciprocating cylindrical pump comprising:

a pump body; a piston slidable in a cylinder defined by said pump body; a fluid inlet and a fluid outlet, and suction and discharge valves; b. an electric motor comprisingi a driving shaft and a cylindrical flange transverse with respect to said shaft,

said shaft projecting from the center thereof;

c. wherein said piston has a length such that the free end thereof extends outwardly of said pump body;

d. means on said pump body to secure it directly onto said cylindrical flange, and

e. an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates, and comprising a suction and discharge conduit block; a pressure circuit in communication with said fluid outlet; a fluid tank; a chamber inwardly of said pump body and a conduit permanently connecting said chamber and said tank; said piston reciprocating in said cylinder to suck fluid from said chamber into said cylinder and discharge it from said cylinder into said discharge circuit; wherein said cylinder in which said piston is displaced forms a cover for said chamber and comprises a housing for said block.

9. A pump-motor set as claimed in claim 8 in which said suction and discharge conduits of said block form seats for said suction and discharge valves at one end thereof.

10. A pump-motor set according to claim 9 comprising a wide surface filter located as close as possible to the orifices of the conduits connecting said cylinder and said chamber.

11. A pump-motor set as claimed in claim 10 wherein said filter is supported by said cover and elastomeric rings therebetween acting as sealing joints and to secure said filter to said cover.

12. A pump-motor set comprising:

a. at least one reciprocating cylindrical a pump body; a piston slidable in a cylinder defined by said pump body; a fluid inlet and a fluid outlet; and suction and discharge valves; b. an electric motor comprising:

a driving shaft and a cylindrical flange transverse with respect to said shaft,

said shaft projecting from the center thereof;

c. wherein said piston has a length such that the free end thereof extends outwardly of said pump body;

d. means on said pump body to secure it directly onto said cylindrical flange, and

e, an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates, and

f. wherein said motor is provided with a forward bearing adjacent to said flange for the support of said shaft and wherein the stroke of said piston is substantially equal to 2.5 times the ratio of the starting torque to the permissible force that said roller will allow on said free end of said shaft.

pump comprising: 

1. In a reciprocating cylindrical pump for use with an electric motor having a casing formed with a cylindrical annular flange portion and a motor drive shaft journaled in bearings included in the casing and extending centrally of said flange portion, said pump having a body formed with a cylinder, a piston slidable in said cylinder, a fluid inlet, a fluid outlet and suction and discharge valves, the improvement comprising: a. said piston having a length such that the free end thereof extends outwardly of said pump body; b. means on said pump body to secure it directly onto said cylindrical flange, and c. an eccentric to be mounted directly on said motor shaft for reciprocating said piston as said shaft rotates.
 2. A pump as claimed in claim 1 wherein said pump body has outer surfaces having a shape mating the shape of said motoR flange; said surfaces constituting at least one portion of said means for positioning and directly securing said pump on said motor flange.
 3. In a reciprocating cylindrical pump for use with an electric motor having a cylindrical flange and a drive shaft extending centrally of said flange, said pump having a body formed with a cylinder, a piston slidable in said cylinder, a fluid inlet, a fluid outlet and suction and discharge valves, the improvement comprising: a. said piston having a length such that the free end thereof extends outwardly of said pump body; b. means on said pump body to secure it directly onto said cylindrical flange; and c. an eccentric to be mounted directly on said motor shaft for reciprocating said piston as said shaft rotates; d. wherein said pump body has outer surfaces having a shape mating the shape of said motor flange; e. said surfaces constituting at least one portion of said means for positioning and directly securing said pump on said motor flange; and f. wherein said means for directly securing said pump body on said motor flange further comprises two lugs each drilled with a hole, the said holes being spaced by 90* in relation to the axis of the motor and wherein a bearing surface for said pump body on said flange is provided between said lugs.
 4. A pump-motor set comprising: a. at least one reciprocating cylindrical pump comprising: a pump body; a piston slidable in a cylinder defined by said pump body; a fluid inlet and a fluid outlet, and suction and discharge valves; b. an electric motor comprising: a driving shaft and a casing having bearings therein journaling said shaft, said casing including a cylindrical flange transverse with respect to said shaft, said shaft projecting from the center thereof; c. wherein said piston has a length such that the free end thereof extends outwardly of said pump body; d. means on said pump body to secure it directly onto said cylindrical flange, and e. an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates.
 5. A pump-motor set as claimed in claim 4 wherein said eccentric is keyed directly onto the free end of said shaft and comprising a ball bearing mounted over said eccentric with means for the axial adjustment of said eccentric on said shaft; said adjusting means being constituted by means for mounting the said eccentric on said shaft to provide rotation thereof in unison.
 6. A pump-motor set as claimed in claim 5 wherein said means for the axial adjustment and rotation mounting means comprise two setscrews threaded through said eccentric to bear against the free end of said shaft.
 7. A pump-motor set as claimed in claim 6 in which said two setscrews bear against the outer cylindrical surface of said free end of said shaft.
 8. A pump-motor set comprising: a. at least one reciprocating cylindrical pump comprising: a pump body; a piston slidable in a cylinder defined by said pump body; a fluid inlet and a fluid outlet, and suction and discharge valves; b. an electric motor comprising: a driving shaft and a cylindrical flange transverse with respect to said shaft, said shaft projecting from the center thereof; c. wherein said piston has a length such that the free end thereof extends outwardly of said pump body; d. means on said pump body to secure it directly onto said cylindrical flange, and e. an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates, and comprising a suction and discharge conduit block; a pressure circuit in communication with said fluid outlet; a fluid tank; a chamber inwardly of said pump body and a conduit permanently connecting said chamber and said tank; said piston reciprocating in said cylinder to suck fluid from said chamber into said cylinder and discharge it from said cylinder into said discharge circuit; wherein saId cylinder in which said piston is displaced forms a cover for said chamber and comprises a housing for said block.
 9. A pump-motor set as claimed in claim 8 in which said suction and discharge conduits of said block form seats for said suction and discharge valves at one end thereof.
 10. A pump-motor set according to claim 9 comprising a wide surface filter located as close as possible to the orifices of the conduits connecting said cylinder and said chamber.
 11. A pump-motor set as claimed in claim 10 wherein said filter is supported by said cover and elastomeric rings therebetween acting as sealing joints and to secure said filter to said cover.
 12. A pump-motor set comprising: a. at least one reciprocating cylindrical pump comprising: a pump body; a piston slidable in a cylinder defined by said pump body; a fluid inlet and a fluid outlet; and suction and discharge valves; b. an electric motor comprising: a driving shaft and a cylindrical flange transverse with respect to said shaft, said shaft projecting from the center thereof; c. wherein said piston has a length such that the free end thereof extends outwardly of said pump body; d. means on said pump body to secure it directly onto said cylindrical flange, and e. an eccentric secured directly on said motor shaft for reciprocating said piston as said shaft rotates, and f. wherein said motor is provided with a forward bearing adjacent to said flange for the support of said shaft and wherein the stroke of said piston is substantially equal to 2.5 times the ratio of the starting torque to the permissible force that said roller will allow on said free end of said shaft. 